List custom agents as slash commands with a prefix.

[gayanper]

Describe the feature or problem you'd like to solve

Selecting a custom agent requires two steps, this cannot be represented in ACP protocol.

Proposed solution

The proposed solution is to make the custom agent commands available as slash commands with a prefix to separate them. For example if the user has following custom agents

• review-tests
• java-review

Those custom agents will be able as slash commands through agent input and ACP available commands as

• agent::review-test
• agent::java-review

For CLI users this makes is easy to select custom agents with one selection. and the same can be easily make available through available commands in ACP model.

Example prompts or workflows

No response

Additional context

No response

[agoncal]

Anthropic introduced skills as slash commands. If Copilot CLI does the same (#1744) (and also reference prompts #1334 and #618), then would we do the same for skills and prompts?

• agent::review-test
• agent::java-review
• skill::cli-changelog
• skill:create-pr
• prompt::bootstrap-project
• prompt::write-review